The present invention relates to a combustion pressure sensor which includes a housing, a displacement member which is displaced with pressure received from an axially forward side, and a connection member which elastically connects the housing and the displacement member, and to a glow plug with combustion pressure sensor. The invention also relates to methods of manufacturing the combustion pressure sensor and the glow plug with combustion pressure sensor.
A known combustion pressure sensor detects combustion pressure of an internal combustion engine such as a diesel engine.
For example, International Publication No. WO/2006/072514 discloses such a combustion pressure sensor (glow plug with combustion pressure sensor) having a tubular plug body (housing), a heater member (displacement member) which receives combustion pressure of an internal combustion engine and is displaced in the axial direction of the plug body with the combustion pressure, and a tubular membrane (connection member) which is welded to the heater member and to the plug body and holds the heater member in an axially elastic manner. FIG. 3 of International Publication No. WO/2006/072514 shows a combustion pressure sensor in which a membrane 36 and a heater member 38 are welded through a weld 58, and the membrane 36 and a plug body 12 are welded through a weld 62.
In a condition before welding, the housing and the connection member, or the displacement member and the connection member may radially separate from each other at least partially in a circumferential direction due to the difference in diameter therebetween.
In this condition, when an energy beam is radiated toward the connection member from outside the connection member in order to weld the connection member and the housing, molten metal derived from the connection member and the housing is consumed in filling a gap therebetween. As a result, the amount of metal of the weld for welding the connection member and the housing reduces, potentially resulting in a failure to firmly weld the members. Similarly, in welding the connection member and the displacement member, molten metal derived from the connection member and the displacement member is consumed in filling a gap therebetween. As a result, the amount of metal of the weld for welding the members reduces, potentially resulting in a failure to firmly weld the members.
The present invention has been conceived in view of the above problem, and an object of the invention is to provide a combustion pressure sensor in which a connection member and a housing, or a connection member and a displacement member are firmly welded and to provide a glow plug with combustion pressure sensor, or a combustion pressure sensor which doubles as a glow plug, as well as a method of manufacturing the combustion pressure sensor and a method of manufacturing the glow plug with combustion pressure sensor.